Tuberkulintest

The Tuberkulintest, commonly known as the tuberculin skin test (TST) or Mantoux test, is a diagnostic procedure used to determine whether an individual has been infected with *Mycobacterium tuberculosis*, the bacterium responsible for tuberculosis (TB). The test relies on the body’s immune response to tuberculin, a purified protein derivative (PPD) derived from the tuberculosis bacillus.

During the test, a small amount of PPD is injected intradermally into the inner forearm, creating a raised bump. After 48 to 72 hours, a healthcare professional measures the size of the resulting induration (a hardened, swollen area) rather than redness. A positive reaction—typically indicated by an induration of 5 mm or more—suggests prior exposure to *M. tuberculosis* or, in some cases, the BCG vaccine, which is used to prevent tuberculosis in children.

The TST is widely used in screening programs, particularly in high-risk populations such as healthcare workers, immunocompromised individuals, and those with close contact to TB patients. However, it is not foolproof, as false positives can occur due to cross-reactivity with other mycobacteria (e.g., from environmental exposure) or BCG vaccination. Conversely, false negatives may result from recent TB infection, immunosuppression, or improper test administration.

While the TST remains a valuable tool, newer diagnostic methods like the interferon-gamma release assays (IGRAs) are increasingly used for more accurate differentiation between latent TB infection and BCG vaccination effects. The test is generally safe, with minor side effects such as redness, itching, or swelling at the injection site. However, individuals with severe allergies to PPD components should avoid the test. Proper interpretation requires clinical correlation, as a positive result does not definitively confirm active TB disease, which may require further diagnostic evaluation.